The present invention relates to new aromatic diamines. More particularly, the present invention relates to new aromatic diamines prepared from cashew nut shell liquid (CNSL), which is a renewable resource material. The present invention particularly relates to novel 1,1-bis(4-aminophenyl)-3-alkylcyclohexanes and to a method for their preparation.
Cashew nut shell liquid (CNSL) is known to contain compounds useful in several areas of chemical industry, such as plastics production. The level of interest in CNSL is evident by the fact that technical grade CNSL is a commercially available product. CNSL comprises a major proportion (typically about 80% by wt) of a material sold commercially under the trade name CARDANOL which comprises a mixture of 3-(pentadec-8-enyl)phenol, 3pentadec-8,11-dienyl)phenol and 3-(pentadec-8,11,14-trienyl)phenol. Minor constituents include about 18% by wt. of a material also sold separately under the trade name CARDOL, which is a mixture of the corresponding 5-substituted resorcinols, and about 2% by wt. of 2-methylcardol, which is a mixture of the corresponding 2-methyl-5-substituted resorcinols, and other materials.
The development of new aromatic diamines which are capable of providing polymers with high processability and are also useful in applications such as interlayer dielectrics, alignment liquid crystal films and light wave guide materials is an area of importance. It is known in the art that incorporating long alkyl chain in polyimide backbone provides materials with application in alignment liquid crystal films. It is therefore of great interest to synthesize new diamines with alkyl radical in their structure. It is also of importance and interest to develop aromatic diamines, which are easily and economically obtained from CNSL, since CNSL is readily available commercially and is also a renewable resource.
The main object of the invention is to provide new aromatic diamines from naturally occurring materials such as cashew out shell liquid.
It is another object of the invention to provide a class of novel 1,1-bis(4-aminophenyl)-3-alkylcyclohexanes, from naturally occurring materials such as cashew nut shell liquid.
It is another object of the invention to provide a process for the preparation of a class of novel 1,1-bis(4-aminophenyl)-3-alkylcyclohexanes, from naturally occurring materials such as cashew nut shell liquid.
It is another object of the invention to provide a simple process for synthesis of novel aromatic diamine starting from naturally occurring cashew nut shell liquid (CNSL) which is capable of providing processable polyimides, polyamides, polyazomethines and the like.
The present invention provides novel aromatic diamines synthesized from naturally occurring and renewable resources such as CNSL, which have application in manufacture of processable polymers polyimides, polyamides, polyazomethines and the like.
Accordingly, the present invention provides a 1,1-bis(4-aminophenyl)3-alkylcyclohexane of the formula I 
wherein R is an alkyl radical with at least 8 carbon atoms.
In one embodiment of the invention, R is pentadecyl.
The present invention also relates to a process for the preparation of 1,1-bis(4-aminophenyl)-3-alkylcyclohexane of the formula I. 
wherein R is an alkyl radical with at least 8 carbon atoms, said process comprising:
(a) hydrogenating a composition comprising substituted phenols of the formula II 
wherein Rxe2x80x2 is an alkyl or alkenyl radical containing at least 8 carbon atoms, to the corresponding substituted cyclohexanols;
(b) oxidizing the substituted cyclohexanols to corresponding cyclohexanones; and
(c) reacting the cyclohexanones obtained in step (b) with aniline in the presence of an acidic catalyst to obtain the compound of formula I.
In one embodiment of the invention, Rxe2x80x2 is selected from the group consisting of pentadecyl, C15 mono-olefinic radical, C15 di-olefinic radical, C15 tri-olefinic radical and any mixture thereof.
In another embodiment of the invention, the composition of step (a) is cashew nut shell liquid.
In another embodiment of the invention, step (A) is carried out at a temperature in the range of 120-150xc2x0 C. and a pressure in the range of 500-700 psi, in the presence of a Group VIII metal catalyst.
In yet another embodiment of the invention, the Group VIII metal is ruthenium.
In yet another embodiment of the invention, the oxidation of step (b) is carried out using an oxidizing agent selected from the group consisting of hexavalent chromium compound, a peroxide and molecular oxygen.
In another embodiment of the invention, the oxidising agent is pyridinium chlorochromate.
In still another embodiment of the invention, step (b) is carried out at room temperature.
In another embodiment of the invention, the acidic catalyst used in step (c) is selected from acidic clay and hydrogen chloride.
In still another embodiment of the invention, step (c) is carried out at a temperature in the range of 140-160xc2x0 C.
The present invention also relates to a process for the preparation of 1,1-bis(4-aminophenyl)-3-pentedecylcyclohexane, comprising:
(a) hydrogenating a composition comprising 3-pentadecylphenol obtained from cashew nut shell liquid to 3-pentadecylcyclohexanol, in the presence of a ruthenium catalyst,
(b) oxidizing 3-pentatecylcyclohexanol to 3-pentdecylcyclohexanone with an oxidizing agent;
(c) reacting 3pentdecylcyclohexanone with aniline in the presence of an acidic catalyst to obtain 1,1-bis(4-aminophenyl)3-pentedecylcyclohexane.
In another embodiment of the invention, step (a) is carried out at a temperature in the range of 120-150xc2x0 C. and a pressure in the range of 500-700 psi.
In yet another embodiment of the invention, the oxidizing agent is selected from the group consisting of hexavalent chromium compound, a peroxide and molecular oxygen.
In another embodiment of the invention, the oxidising agent is pyridinium chlorochromate.
In still another embodiment of the invention, step (b) is carried out at room temperature.
In another embodiment of the invention, the acidic catalyst used in step (c) is selected to from acidic clay and hydrogen chloride.
In still another embodiment of the invention, step (c) is carried out at a temperature in the range of140-160xc2x0 C.